Musnad Ahmad 30:911

'Abd al-Rahman narrated to us, Zuhayr narrated to us, from al-'Ala' ibn 'Abd al-Rahman, from his father, from Abu Hurayrah, from the Prophet, peace and blessings of Allah be upon him, who said: "Hasten to perform deeds before tribulations come like pieces of a dark night. A man will wake up as a believer and go to sleep as a disbeliever, and he will go to sleep as a believer and wake up as a disbeliever, selling his religion for a small portion of the world."